Abstract
Interest in some non-Saccharomyces yeasts has increased recently, because they have been associated with an improvement in wine quality. Nevertheless, little attention has been paid to the effect that the use of these yeasts may have on malolactic fermentation (MLF). In this study, the strains Torulaspora delbrueckii Biodiva and Metschnikowia pulcherrima Flavia were evaluated by co-inoculation and sequential fermentation with S. cerevisiae QA23. A fermentation with S. cerevisiae as a single starter was also performed as a control, then MLF was performed inoculating Oenococcus oeni PSU-1 in all wines. Finally, the wines obtained after alcoholic fermentation and MLF were characterised. The results of the coinoculated fermentations were similar to those of the S. cerevisiae control fermentations. Nevertheless, significant differences were observed in sequential fermentations in terms of lower content of acetic, L-malic and succinic acids. These differences were particularly noticeable in fermentations carried out with T. delbrueckii.
Highlights
This study shows that the impact of non-Saccharomyces was greater on sequential alcoholic fermentations (AF) than on coinoculated AF
When T. delbrueckii was used, it had a positive effect on O. oeni and Malolactic fermentation (MLF) due to lower acidity, succinic acid and SO2, even though MLF was slightly slower than in S. cerevisiae wines
M. pulcherrima decreased ethanol content during AF, which minimised its negative effect on O. oeni, yet MLF was slower than in control wines
Summary
There has been an increasing interest in inoculating grape musts with non-Saccharomyces yeasts to complement the traditional usage of Saccharomyces cerevisiae as a sole starter, as they improve product quality and complexity (Ciani et al, 2010; Comitini et al, 2011; Contreras et al, 2014; Jolly et al, 2003, 2014; Whitener et al, 2015; Zott et al, 2011) These other yeast species have little or moderate fermentation power and S. cerevisiae must be inoculated to finish the alcoholic fermentations (AF) (Benito et al, 2015). In addition to decreasing wine acidity, MLF induces other changes such as microbiological stability or organoleptic improvement (Bartowsky, 2005)
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